Method for purifying fatty oils and fats



3,008,972 METHOD FOR PURIFYING FATTY OILS AND FATS Mitsuo Mitani, 223, l-Chome, Totsnka-cho, Shinjuku-ku, Tokyo, Japan No Drawing. Filed Mar. 31, 1958, Ser. No. 724,788 Claims priority, application Japan Apr. 20, '1957 7 Claims. (Cl. 260-425) The present invention relates to a method for purifying fatty oils and fats which contain a free fatty acid in order to remove the free fatty acid from the said fatty oils and fats. The soap which is formed at the time of neutralizing fatty oils and fats-containing free acid with alkali emulsifies the water and the oil derived from the said fatty oils and fats toiform inseparable mixture. The inventor of the present invention found that at the timeof purifying fatty oils and fats, the presence of phosphoric acid ion or ammonium ion prevents the emulsification without being effected by the presence of other salts in the fatty .oils and fats and enables the separation of oil and soap solution, and also the inventor found that even with a salt such as potassium chloride, sodium chloride, potassium nitrate, sodium nitrate or the like which does not form insoluble soap, if pH of the solution which was obtained by reacting dilute alkaline solution with fatty oils and fats under the said salt is adjusted to be within a certain range of values, the formed soap is in-aqueous solution and may be separated without emulsifying oils even when using no phosphoric or ammonium ion as mentioned in the above, and that if this invention be utilized, the great loss of neutral oil as a result of forming so-called alkali-foots contained in soap, which was inevitable in the conventional oil purification, is minimized to the utmost.

When fatty oils and fats which contain free fatty acid are reacted with alkali and phosphoric acid ion or ammonium ion together with a large amount of water and left at a temperature of over 70 C., then they separate into two layers or three layers. In case of twolayers, the upper phase is oil and lower phase is micelle solution which is formed by the dispersion of the micelle of soap into the aqueous solution of the said salts. In case of three layers, under the phase of the above-mentioned micelle solution the true solution of soap contained in the aqueous solution of the salts is separated.

As a rule, the boundaries of these layers are very clear and when the pH valuesof both soap micelle solution and the true solution of soap at the time of separation are measured under the room temperature, the pH value of 7.5-9.5 was obtained for the true solution and the pH value of micelle solution was about 0.2-0.5 higher than that of the true solution.

In case phosphoric ion and ammonium ion are used in proper amount, the pH is automatically adjusted due to bufieraction and therefore the "amount of alkali to be used need not be restricted. However, in case separation is elfected not by the use of these ions but other salts as mentioned in the above, for example if caustic potash is used as alkali, the theoretical neutralization value of the canst-ic potash should be kept below 80%, otherwise the saponaceous solution emulsifies fatty oils and fats and makes separation impossible. Between the ratio of the theoretical neutralization value (cc) to the amount of alkali used in the above-mentioned case and the minimum amount of salts ([KClJ) enough to prevent emulsifica- -tion, the relation of log KCloom is established and when inite tates Patent 3,008,972 Patented Nov. 14, 1961 ice corresponding to the amount of alkali, the smaller the amount of alkali is to the theoretical value, the greater becomes the amount of fatty acid to be separated by alkali of a unit amount. That is, in case of KOI-I and KC], if the amount .of KOH used is'5 0% of the theoretical value, the amount of fatty acid to be excluded reaches about 150% of the amount corresponding to the amount of KOH, and when the amount of KOH is about of the theoretical value, the amount .of fatty acid to be excluded becomes approximately 125% against the amount of KOH.

The reason why soap solution and fatty oils and fats are separated by the presence of the salts and with proper pH value with no suspension left into the different layers is considered to be due to the influence of the solubilisation of fatty oils and fatsagainst the aqueous soap solution with the presence of not only normal soap, but also acid soap and salts and also the influence of interfacial tention with as much pH values as obtained in the above. However, these :matters belong :to the frontiers in colloid chemistry and .are difficult for their complete explanation. It is a fact, however, that by utilizing the method of the present invention :the fatty oils and fats containing much of free fatty acid can be separated into neutral oil and fatty acid with substanitally higher .efliciency than by the formerly used conventional method.

The detailed explanation of the present invention will be made in the following with reference to working examples:

Example 1 about cc. each time until .finally the washing water remains clear, an-d 59 g. of oil with acid value .of .18 was obtained.

Example 2 .Rice bran .oil 100g. with acid valne'T/O wasadded with water 350 cc., methanol cc., 5-0 cc. of aqueous solution of 10% sodium hydroxide and 30 g. of ammonium phosphate and .after reacted under the temperature of 70-80 .C. applied with the-same treatmentasin Example 1 and 55 g. of oil with acid value of .16 wasrobtain ed.

Example ,3

The mixture of water 350 cc., ammonium phosphate 15 g. :and 70cc. of aqueous solution of 10% apotassiumhydroxide is kept under the temperature of 70 C..and added with 100 g. of rice bran oil with acid value of 70, and then after being reacted while stirring raising the tem- "perature until 92 'C., the mixture is applied with the same "treatment as in the previous example.

Thus, 55 g. of oil was obtained and acid value was 26.5.

Example 4 .Rice bran oil .100 ,g. with acid value of 70 was .added with 400 c.c. of water and 15 cc. of aqueous solution of 28% ammonia, stirred under the temperature of .70 6.,

and added with .15 g. of ammonium phosphate and the temperature was raised until 95 C. and .then with the same treatment as in the previous examples 63 got oil with :acid value of 13 was obtained.

The saponaceous solution 'which was left over after .the separation of oil was acidified with sulfuric acid,

heated with the temperature of 90 C. and stirred, and

The fatty acid was separated and 34 g. of fatty acid with acid value of 180 was obtained.

Example 5 The oil 100 g. with acid value of 60 which was obtained by acidifying alkali-foots of rape seed oil with sulfuric acid was added with 400 cc. of water, 13 cc. of 28% ammonia water and 16.5 g. of ammonium phosphate stirred at temperature of 90-95 C. and the same treamtent as in the previous examples was applied, thus 70 g. of oil With acid value of 10.5 was obtained.

Example 6 Rice bran oil 100 g. with acid value of 70 was mixed with water 350 cc., aqueous solution of 14% sodium hydroxide 31.5 cc. and ammonium phosphate 14 g., reacted together at the temperature of 65-90 C., and was left standing at a temperature of 8090 C. After washing the oil with water, 60 g. of oil with acid value of 15 was obtained.

Example 7 Rice bran oil 100 g. with acid value of 70 was mixed with water 350 cc. and aqueous solution of 10% sodium hydroxide 400 cc., stirred at a temperature of 8085 C., and then mixed with sodium sulfate 54 g. and ammonium phosphate 8 g. and after being stirred at a temperature of over 90 C. was left standing. The oil was thus separated and washed with water and 60 g. of oil with acid value of L1 was obtained.

Example 8 Rice bran oil 100 g. with acid value of 70 was mixed with water 350 cc. and aqueous solution of 14% sodium hydroxide 27 cc. and while stirring at a temperature of 8085 C. was mixed with sodium chloride 15 g. and ammonium oxalate 7 g. and after being stirred at a temperature of 85-90 C. was left standing to separate oil. The oil thus obtained was washed with water and 54 g. of oil with acid value of 14 was obtained.

Example 9 Rice bran oil 100 g. with acid value of was mixed with water 200 cc., aqueous solution of 14% sodium hydroxide 9.5 cc. and ammonium phosphate 2 g., and was stirred at a temperature of 85 C. and was left standing. The oil thus separated was washed with water and 83 g. of oil with acid acid value of 6.2 was obtained.

Example 10 Example 11 Rice bran oil 100 g. with acid value of 43 which was obtained by filtering wax under the temperature of about 40 C. was heated and added with the solution of water 150 cc. with 10 g. of ammonium sulfate, g. of hydrated Glaubers salt and 14.8 cc. of aqueous solution of 17.7% sodium hydroxide while stirring at a temperature of 7585 C. for 2 minutes and left standing in the water bath of 90 C. for 15 minutes where it separated into three layers.

The oil layer was 77 g. and the acid value lowered to 8.3. Saponified solution was 107 g. and pH value of the three solution of soap of the lower layer was 8.5 as measured with glass electrode at a temperature of 31 C. The amount of crude fatty acid obtained by separating saponified solution with sulfuric acid was 22.5 g. and the acid value was 160.

In case of rice bran oil, the oil with acid value of 70 contains about 35% of free fatty acid, and therefore in the afore-mentioned Example 4, 93 came out as purified oil. Compared with the conventional method where with acid value of about 60 almost all amount of oil becomes foots oil and no neutral oil can be obtained. Accordingly, the method of the present invention yields results of marked difference.

Example 12 Case 1.Dewaxed rice bran raw oil 50 g. with acid value of 48 was added to water 90 cc. and mixed and reacted with 14 cc. of aqueous solution of KOH with 85 mg. in 1 cc. in proportion, that is 50% of the theoretical value, and further mixed with the solution of 2 g. KCl in 5 cc. water and stirred at a temperature of C. C. The resulting mixture goes into gel form and does not separate. However, when the solution of KCl was added gradually until the amount of KCl added be came 2.9 g., and the mixture was stirred for a few minutes and left standing at a temperature of 85 C.- C. for about 10 minutes, then is separated into two layers with the upper phase for the oil with lowered amount of free acid and with the lower phase for the micelle solution of soap.

The acid value of the oil layer was 15.3. The quantity of oil layer was 40 g. Decreased amount of free fatty acid reached as high as 75% and free acid 1.5 times in amount of the alkali used was separated from oil as the micelle solution of soap.

Case 2.The saponaceous solution and oil of case 1 were again mixed, mixed with 4 cc. of the same aqueous solution of KOH as mentioned in the above case 1 and stirred and made in gell form. As in the afore-mentioned case 1, KCl was gradually added and the necessary amount of KCl for the separation was obtained to be 4.4 g. The total amount of KCl used in case 1 and case 2 was 7.3 g. and the obtained acid value of the oil at the time was 10.

Case 3.2 cc. of the same aqueous solution of KOH ,as mentioned in said case 1 was further added to the product of case 2.

The minimum necessary amount of KCl was obtained to be 6.7 g. The total amount of KCl from the beginning since case 1 was 14 g. and the acid value became lowered to 7.4.

Case 4.In the same way, when 1 cc. of the said aqueous solution of KOH was added, 5 g. KCl was necessary and the acid value of oil was lowered to 6.3.

In this case, separation into three layers took place with the upper phase for oil, the middle phase for micelle solution of soap and the lower for the true aqueous solution of soap against the aqueous solution of KCl. The pH value of the lower phase was 8.35 under the normal temperature.

Case 5 .In the same way, the product of case 4 was added with 1.7 cc. of the said aqueous solution of KOH and cc. of water and when 15.5 g. of KCl was added separation was formed into three layers. The acid value of oil was 4.8 and the pH value of the lower phase was 8.65 under the normal temperature.

As clearly seen in the results of the above series of experiments, the necessary amount of KCl rapidly increases in accordance with the increase of the amount of KOH. This relation roughly satisfies the following relation:

Log (necessary amount c0 of KCl) (Ratio of the amount of KOH used to the theoretic a1 neutralization value).

The total amount of KOH used from case 1 to case 5 was 80% of the theoretical neutralization value and the total amount of KCl was 34.5 g.

Example 13 Dewaxed rice bran raw oil 50 g. with acid value of 48 was added with 100 cc. of water and as in Example 12 an experiment was performed as to NaOH and NaCl. The result was that the amount of NaOH and the necessary amount of NaCl were in logarithmic relation.

Example 14 Case 1.-Dewaxed lice bran raw oil g. with acid value of 48 was mixed with water 180 cc., further mixed with 5.6 cc. of aqueous solution of NaOH 220 g.l., that is, 70% of the theoretical neutralization value, and again added with 6 g. of NaCl and 0.5 g. of NaH PO 2H O and stirred under the temperature 80 .C.-90 C. for 3 minutes and was left standing where it separated into 2 layers. The acid value of the oil layer became lowered to be 97.2 and the needed amount was 37 g. I Case 2.'35 g. of oil with acid value of 9.2 obtained in case 1 was mixed with water 60 cc., 0.6 cc. of aqueous solution of NaOH 220 g./ 1., that is 60% of the theoretical neutralization value and further mixed with 1 g. of NaCl and 0.1 g. of Na HPO .12H O and stirred at the temperature of 85 C. for 3 minutes and left standing to separate into two layers. The oil layer was 30.5 g. with acid value of 2.4.

Example Dewaxed rice bran raw oil 50 g. with acid value of 48 was mixed with 5 cc. of aqueous solution of NaOH 220 g./l., that is, 65% of the theoretical neutralization value,

Dewaxed r-ice bran raw oil 50 g. with acid value of 48 was mixed with 5 g. of NaOH;, and 90 cc. of water and heated at above 70 C., again mixed with 4.2 cc. of aqueous solution of NaOH 220 g./l. and stirred for 6 minutes and left standing to be separated into 3 layers. 37 g. of oil with acid value of 14.5 was obtained. The pH of the aqueous solution of ions was 8.0 at C.

As clearly seen in the above examples from 12 to 16, even in the method of the said five examples, the yielded percentage of oil reached as high as 93, and without the presence of ammonia or phosphoric ion, fatty oils and fats can be separated with high efliciency, which can never be attained by the conventional method.

The fatty acid obtained :by acidifying the saponified solution by the method of the present invention has the purity of as much as 90% and by directly distilling the fatty acid pure fatty acid can be obtained.

The oils and fats with high acid value which were less evaluated for the reason that they were impossible to separate free acid by the method formerly used can separate neutral oil and free fatty acid to be purified by applying a simple treatment of the present invention.

What I claim is:

1. A method for purifying fatty oils and fats which comprises treating said fatty oils and fats containing free fatty acid with an alkali in an amount less than the amount required to neutralize fat free fatty acids, water in an amount sufiicient to dissolve the formed soap as a micelle solution and a substance, selected from the group consisting of ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate and ammonium sulfate which yields in water an ion selected from the group consisting of phosphate ion and ammonium ion under the condition that the pH of the 6 formed micelle solution is in a range of between 7.7-9.7, and thereafter separating the free fatty acid from the oil as a micelle solution of said soap while preventing emulsification by the soap.

2. A method for purifying fatty oils and fats which comprises treatintg said fatty oils and fats containing free fatty acids with an alkali in an amount less than the amount required to neutralize fat free fatty acids, water in an amount sufficient to dissolve the formed soap as a micelle solution and a substance, selected from the group consisting of ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate and ammonium sulfate which yields in water an ion selected from the group consisting of phosphate ion and ammonium ion under the condition that the pH of the formed micelle solution is in a range of between 779.7, and thereafter separating the free fatty acid from the oil at a temperature of at least 70 C. as a micelle solution of said soap while preventing emulsification by the soap.

3. A method for removing the free fatty acid from oil contained in fatty oils and fats which comprises neutralizing said oils and fats containing the free acid with an aqueous solution of an alkali in an amount less than the amount required to neutralize fat free fatty acids, and then adding to said neutralized oils and fats a substance, selected from the group consisting of ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate and ammonium sulfate which yields in water an ion selected from the group consisting of phosphate ion and ammonium ion, and water in an amount sufiicient to dissolve the formed s'oap as a micelle solution, the pH of said micelle solution being within the range of 7.79.7, and thereafter separating the free fatty acid from the neutral oil at a temperature of at least 70 C. as a micelle solution of said soap while preventing emulsification by the soap.

4. A method for removing the free fatty acid from oil contained in oils and fats which comprises neutralizing the said oils and fats containing free acid with an aqueous soltuion of an alkali in an amount less than the amount required to neutralize fat free fatty acids, adding to said neutralized oils and fats a substance, selected from the group consisting of ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate and ammonium sulfate which yields in water an ion selected from the group consisting of phosphate ion and ammonium ion, water in an amount sufiicient to dissolve the formed soap as a micelle solution, and another salt which does not yield in water phosphate ion and ammonium ion, the pH of said micelle solution being within the range of 7.7-9.7, and thereafter separating the free fatty acid from the neutral oil at a temperature of at least 70 C. as a micelle solution of said soap while preventing emulsification by the soap.

5. A method for removing the free fatty acid from oil contained in oils and fats containing free acid with an aqueous solution of an alkali in an amount less than the amount required to neutralize fat free fatty acids, adding to said neutralized oils and fats a substance, selected from the group consisting of ammonium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate and ammonium sulfate which yields in water an ion selected from the group consisting of phosphate ion and ammonium ion, water in an amount sufficient to dissolve the formed soap as a micelle solution, and an alcohol, the pH of said micelle solution being within the range of 7.7-9.7, and thereafter separating the free fatty acid from the neutral oil at a temperature of at least 70 C. as a micelle solution of said soap while preventing emulsification by the soap.

6. A method for purifying fatty oils and fats which comprises adding to said fatty oils and fats containing free fatty acid an alkali in an amount less than the amount required to neutralize said free fatty acid, water in an amount sufiicient to dissolve the formed soap as a micelle solution, and a salt, selected from the group consisting of potassium chloride, sodium chloride, potassium nitrate, sodium nitrate and sodium sulfate, in an amount sufiicient to destroy the emulsion, the pH of said micelle solution being within the range of 7.7 to 9.7, and thereafter separating the free fatty acid from the neutral oil at a temperature of at least 70 C. as a micelle solution of said soap while preventing emulsification by the soap.

7. A method for purifying fatty oils and fats which comprises adding to said fatty oils and fats containing free fatty acid an alkali in an amount less than the amount required to neutralize said free fatty acid, Water in an amount sufficient to dissolve the formed soap as a micelle solution, and a salt, selected from the group consisting of potassium chloride, sodium chloride, potassium nitrate, sodium nitrate and sodium sulfate, in an amount sufi'icient to destroy the emulsion, the pH of said solution being within the range of 7.7 to 9.7, and thereafter separating at a temperature of at least 70 C. fatty oils and fats containing a lesser amount of free fatty acid than that of the starting fatty oils and fats, repeating the above-mentioned operation more than twice, whereby a substantial amount of the free fatty acid is removed from the fatty oils and fats.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD FOR PURIFYING FATTY OILS AND FATS WHICH COMPRISES TREATING SAID FATTY OILS AND FATS CONTAINING FREE FATTY ACID WITH AN ALKALI IN AN AMOUNT LESS THAN THE AMOUNT REQUIRED TO NEUTRALIZE FAT FREE FATTY ACIDS, WATER IN AN AMOUNT SUFFICIENT TO DISSOLVE THE FORMED SOAP AS A MICELLE SOLUTION AND A SUBSTANCE, SELECTED FROM THE GROUP CONSISTING OF AMMONIUM PHOSPHATE, SODIUM MONOHYDROGEN PHOSPHATE, SODIUM DIHYDROGEN PHOSPHATE AND AMMONIUM SULFATE WHICH YIELDS IN WATER IN ION SELECTED FROM THE GROUP CONSISTING OF PHOSPHATE ION AND AMMONIUM ION UNDER THE CONDITION THAT THE PH OF THE FORMED MICELLE SOLUTION IS IN A RANGE OF BETWEEN 7.7-9.7, AND THEREAFTER SEPARATING THE FREE FATTY ACID FROM THE OIL AS A MICELLE SOLUTION OF SAID SOAP WHILE PREVENTING EMULSIFICATION BY THE SOAP. 